The invention relates generally to optical bar code scanners, and, more specifically, to stand-mountable bar code scanners that are equipped to operate in a longrange mode and a short range mode of object detection.
Many existing optical bar code scanners utilize an object detection mechanism to determine if an object is in proximity to the optically transmissive window of the scanner. Illustratively, this object detection mechanism may be implemented using an infrared light source and an infrared detector. If an object is detected, the scanner will activate a laser beam source of a bar code detection and decoding mechanism so as to attempt a reading of one or more bar codes on the object. If, during this process, a bar code is not detected and decoded, the scanner will deactivate the laser beam source and wait for another object to enter the field of view of the object detection mechanism. Unless the object detection mechanism detects the presence of another object, the laser beam source will remain deactivated, and, in this state, it will not be possible to read any bar codes. Once the object detection mechanism detects a new object, the process of attempting to read a bar code begins again. The scanner reactivates the laser beam source, thereby permitting one or more bar codes to be detected and decoded.
Problems arise if the scanner is mounted or remains in a position such that the object detection mechanism repeatedly detects the presence of a background object, over and over again, but at no time detects the absence of this object. In such situations, the scanner will fail to detect and decode bar codes. The object detection mechanism has deactivated the laser beam source in response to the background object. The laser beam source will not be reactivated unless the object detection mechanism determines that the background object has been removed.
The foregoing scenario will arise in operational environments where a bar code scanner is aimed at a counter top, or other background object, while mounted in a stand. Examples of background objects include counter surfaces, conveyer belts, stands, brackets, and various other surfaces in and around point-of-sale terminals. Some of these objects, such as counter tops, will remain stationary with respect to the bar code scanner, whereas other objects, such as conveyer belts, will not.
By automatically adjusting the object detection mechanism of a bar code scanner from a long range mode of operation to a short range mode of operation, the scanner will remain capable of detecting and decoding bar codes, even after the object detection mechanism has repeatedly detected the presence of a background object. The techniques of the present invention commence when the bar code scanner is placed in a position where the object detection mechanism has repeatedly detected a background object such as a counter top or conveyer belt. The object detection mechanism is set to the long range mode of operation if it is not already so set. In the case of a stand-mounted scanner, a test is performed to ascertain whether or not the scanner is in its stand, and the method will only proceed once the scanner is resting in the stand. Next, the scanner is programmed to wait for a predetermined amount of time, after which the operational mode of the object detection mechanism is changed from the long range mode to the short range mode. At this time, the object detection mechanism no longer detects the presence of the background object, The scanner will now detect any new objects that enter the field of view of the object detection mechanism, and attempt to read any bar codes which may be present.
The invention and its particular features and advantages will become more apparent from the following detailed description considered with reference to the accompanying drawings.